Thermoplastic resins and blends comprising the same are generally characterized by their many advantageous properties which include optical clarity, high ductility high heat deflection temperatures as well as dimensional stability. As a result of such properties, they are often employed in many commercial applications.
One of the most successful thermoplastics available is the acrylonitrile-butadiene-styrene (ABS) terpolymer. ABS consists of discrete, crosslinked polybutadiene rubber particles which are grafted with poly(styrene-co-acrylonitrile) (SAN) and embedded in a SAN matrix. Interior applications of ABS include instrument panels and knobs while external applications include wheel covers and headlight housings.
It is of increasing interest to prepare thermoplastic resins and blends which, while retaining the above-mentioned advantageous properties, also possess flame retardant properties. Several flame retardant agents have been utilized in an attempt to produce flame retardant thermoplastic resins. For example, alkali metal salts of strong sulfonic acids are commonly used. However, when incorporated into the resin, the resulting polymer is hydrolytically sensitive. Further, when using these salts, it is also necessary to employ drip inhibitors or gas phase flame retardant agents which is not ideal since the former destroys the clarity of the polymer and the latter often creates problems with corrosion and toxicity. As an alternative to the above, phosphorus containing compounds such as triphenylphosphate and brominated compounds such as phenyl ethers have been used. When blended with a base polymer, some flame retardant properties are observed. However, the resulting polymer blends are not desirable since they possess low glass transition temperatures and low impact resistances when compared to the base resin. Additionally, epoxide terminated resins have often been employed in flame retardant compositions. The compositions do, however, display charring and black speck formation after thermal exposure and such charring and black speck formation are believed to be induced by the epoxide termination groups.
Accordingly, the instant invention is directed to novel thermally stable resins and flame retardant polymer compositions comprising the same. Moreover, said thermally stable resins are halogenated and they do not comprise epoxide termination groups.